Saints turned in a sensational six-try showing to shoot down Bath 43-25 at Franklin’s Gardens.
Scores from Christian Day, who got two, George Pisi, Jamie Elliott, Samu Manoa and the hugely impressive George North earned the win.
Stephen Myler added 13 points with the boot as Bath, who had won their previous 11 games, were crushed.
Kyle Eastmond’s score and George Ford’s boot put the visitors 13-0 up inside the first 15 minutes, but they were hampered by prop Paul James’ sin-binning.
And despite second-half scores from Rob Webber and replacement Leroy Houston, they left the Gardens with nothing.
It was another shuddering statement of intent from Saints, who have won won their previous five games against Bath and keep the heat on Saracens at the top.
It was also a huge show of spirit after going behind early on in a fiesty affair.
The first big hit of the game came on referee Luke Pearce, who was floored by Bath hooker Webber and needed treatment.
That inspired bizarre scenes as the Bath players left the field with less than two minutes gone, with fourth official Martin Fox being readied to replace Pearce.
Fox, whose named was greeted with boos from the Saints fans, started how he had ended his last game in charge of Northampton - the defeat at Gloucester in September - giving the opposition a penalty at the scrum.
Ford made the most of it to give Bath a 3-0 lead and they soon stretched that as full-back Anthony Watson’s break gave Eastmond a simple chance to score.
Ford applied gloss to the centre’s try by adding the extras to give his side a 10-0 advantage inside just seven minutes, and Saints fans were left fearing a Leinster-style home humbling.
Bath were well on top in the early scrummaging battle and another penalty gave Ford the chance to extend their lead, which he did.
Saints needed a quick riposte and they got it. Manoa thought he’d scored, but was denied by the TMO, but Bath were reduced to 14 men thanks to James’ offence in the build-up.
Day ensured the home team made their man advantage count as he latched on to Dylan Hartley’s pass to score out wide.
Myler superbly landed the conversion and Saints were back to within six points, finally getting a foothold in the game.
Noise levels and aggression levels started to rise and after North was taken out in the air, Saints used the resulting penalty to push Bath back and score.
A slick move, including a good crossfield kick from Myler and a fine take from Elliott, saw George Pisi profit to touch down acrobatically.
Myler made another conversion with aplomb from out wide and, having been 13-0 down, his team were suddenly ahead.
Saints were on sizzling and another slick move from right to left saw Elliott cleverly pick up Ken Pisi’s neat offload to score the home team’s third try.
The remarkable recovery was added to by another Myler conversion, bringing another roar from the Gardens faithful.
And they had even more to shout about at the start of the second half as Kahn Fotuali’i and George Pisi did good work in the build-up to a second Day score.
Myler added the conversion to the delight of the supporters and Saints had secured a bonus point inside 42 minutes.
Bath were now the ones needing to conjur up a special comeback and, after a good saving kick from North, they got it, as the pack drove Webber over the line.
Ford missed the conversion to leave his team 10 points behind, and they weren’t back in it for long as Manoa latched on to an Elliott pass to fly over the line.
Myler lashed the conversion against the left upright, leaving Saints 33-18 up with 20 minutes to go.
But Bath refused to go quietly and a huge scrum saw No.8 Houston pick up the ball from the back to score.
Ford reduced the deficit to eight points with 12 minutes to go but North’s try and Myler’s conversion and penalty put Saints out of sight, denying Bath even a single point for their efforts.
Saints: K Pisi (Collins 47); Elliott, G Pisi (G Dickson 75), Burrell, North; Myler, Fotuali’i (L Dickson 62); A Waller (E Waller 62), Hartley (c) (Haywood 69), Ma’afu (Mercey 52), Lawes, Day (Dickinson 69), Clark (Dowson 64), Wood, Manoa.
Bath: Watson; Agulla (Abendanon 62), Joseph, Eastmond, Banahan; Ford, Roberts (Stringer 46); James (Catt 58), Webber (Guinazu 62), Perenise (Orlandi 52), Hooper (c) (Day 52), Attwood, Garvey, Louw, Fearns (Houston 46).
Replacements not used: Heathcote.
Referee: Luke Pearce (replaced by Martin Fox inside two minutes)